Inkjet printing technology is used in many commercial products such as computer printers, graphics plotters, copiers, and facsimile machines. One type of inkjet printing, known as “drop on demand,” employs one or more inkjet pens that eject drops of ink onto a print medium such as a sheet of paper. Printing fluids other than ink, such as preconditioners and fixers, can also be utilized. The pen or pens are typically mounted to a movable carriage that traverses back-and-forth across the print medium. As the pens are moved repeatedly across the print medium, they are activated under command of a controller to eject drops of printing fluid at appropriate times. With proper selection and timing of the drops, the desired pattern is obtained on the print medium.
An inkjet pen generally includes at least one fluid ejection device, commonly referred to as a printhead, which has a plurality of orifices or nozzles through which the drops of printing fluid are ejected. Adjacent to each nozzle is a firing chamber that contains the printing fluid to be ejected through the nozzle. Ejection of a fluid drop through a nozzle may be accomplished using any suitable ejection mechanism, such as thermal bubble or piezoelectric pressure wave to name a few. Printing fluid is delivered to the firing chambers from a fluid supply to refill the chamber after each ejection.
To increase print quality and functionality, it is desirable to be able to eject printing fluid of different drop weights from a single printhead. This can be accomplished by designing some of the nozzles in a printhead to eject lower weight drops and other nozzles to eject higher weight drops. However, the different configurations used for the low drop weight nozzles and the high drop weight nozzles make it difficult to optimize overall nozzle performance. For example, the ability to provide adequate refill speeds for the high drop weight nozzles can be compromised by the ability to generate sufficient drop velocity for the low drop weight nozzles, and vice versa. Accordingly, dual drop weight range on a single printhead die is limited by an inherent tradeoff between refill speed and drop velocity.